Flexible multilayer thermoforming films are used to package such food item packages, thereby protecting these articles against external contamination and abuse, and therein providing an attractive package for the article for its eventual sale. In certain instances, it is desirable to hermetically seal food item packages, such as blocks of natural cheese to preserve the food item.
A typical packaging bag has three sides heat-sealed by the bag manufacturer leaving one open side to allow product insertion. After a product is inserted, the bag is typically evacuated and the bag mouth sealed to enclose the product. At one time, the standard method for sealing was to fasten a clip around the mouth of the bag. However, heat sealing techniques are now also commonly employed to produce the final closure of the bag. For example, a bag mouth may be either hot bar sealed or impulse sealed. An impulse seal is made by application of heat and pressure using opposing bars similar to the hot bar seal except that at least one of these bars has a covered wire or ribbon through which electric current is passed for a very brief time period (hence the name “impulse”) to cause the adjacent film layers to fusion bond. Following the impulse of heat the bars are typically cooled (e.g., by circulating coolant) while continuing to hold the bag inner surfaces together to achieve adequate sealing strength.
There is great commercial interest in the packaging industry for a film structure, which provides superior properties such as mechanical strength, optical and gas barrier properties, and thermoformability, for example, while having an easy open peelable seal. However, disadvantages remain with existing technology. One particular problem during heat sealing the film is that of excessively high tear propagation strengths. Although strong heat seals provide protection against unwanted seal failure, such seals also make it difficult for the end user to open the package. Accordingly, there is a need for an improved non-heat shrinkable film for a packaging bag that includes a lap seal readily openable by the end user without the use of a knife or cutting implement, and without uncontrolled or random tearing or rupturing of the packaging materials.